Dermatology Online Journal

Pigmented spindle-cell nevus: A melanoma simulator
Andrea Maurichi MD¹, Marzia Baldi MD¹, Cesare Bartoli MD², Aldo Bono MD¹, Tiziana Camerini PhD³, Daniele Moglia MD¹, Roberto Patuzzo MD¹, Elisabetta Pennacchioli MD¹, Gabrina Tragni MD⁴, Mario Santinami MD¹
Dermatology Online Journal 10 (2): 5

Melanoma Unit¹, Day Surgery Unit², Controlled Clinical Trials Unit³, Pathology and Cytopathology Unit⁴, Istituto Nazionale per lo Studio e la Cura dei Tumori, Milan, Italy. andrea.maurichi@istitutotumori.mi.it

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The clinical differential diagnosis of melanoma presents a formidable challenge even to experienced physicians. The concern of the clinician of missing an early curable melanoma conflicts with his or her desire to avoid unnecessary minor or even major surgery in cases where benign lesions show doubtful features. These issues are particularly evident when considering melanoma simulators, those entities that may be clinically and sometimes histologically confused with melanoma [1, 2, 3].

Pigmented spindle-cell nevus (PSCN) is a benign melanocytic lesion first described by Reed et al. [4]. It is generally considered a separate clinicopathologic entity, even if some authors classify this nevus as a variant of Spitz nevus [5, 6, 7, 8, 9, 10, 11]. PSCN has clinical and histopathologic features that may create difficulty in differentiating it from melanoma. We consider this tumor to be a separate clinical entity from Spitz nevus, and so we chose to focus our interest on its clinical features.

Epiluminescence Microscopy (ELM), a noninvasive technique employed in the clinical diagnosis of pigmented skin lesions, permits a detailed examination of the pigmented structures of the epidermis and dermoepidermal junction. The result is the visualization of morphological features not visible to the naked eye, which enhances the clinical diagnosis of nearly all the pigmented lesions including PSCN [12, 13, 14, 15, 16, 17].

This study presents a clinical and dermoscopic description of 63 consecutive cases of PSCN observed and excised at our institute. It evaluates the improvement led by ELM in the diagnosis of this lesion in order to reduce the number of diagnostic operations in patients bearing PSCN.

Patients and methods

All patients with histologic diagnosis of PSCN observed at the Istituto Nazionale per lo Studio e la Cura dei Tumori of Milan from January 1994 to December 1998 were evaluated. Cases submitted for consultation, cases with diagnostic uncertainty, or cases recoded as Spitz nevi were excluded. In total, 63 lesions in 63 patients (43 females and 20 males) were selected. Those cases, all examined clinically and then excised under local anesthesia in our institute, met the features regarded as histological characteristics of PSCN according to widely accepted criteria [18].

All lesions had a recorded clinical diagnosis that has been coupled with ELM evaluation. ELM was performed with a hand-held monocular microscope equipped with an achromatic lens permitting a magnification of 10×.

The distribution of cases according to site and gender is shown in Table 1. The patients ranged from 5 to 62 years, with a median age of 25 years.

Table 1. Distribution of 63 pigmented spindle cell nevi according to site and gender

Site	Male (%)	Female (%)	Total (%)
Head and neck	2 (3.2)	1 (1.6)	3 (4.8)
Trunk	9 (14.3)	8 (12.7)	17 (27.0)
Upper extremity	5 (7.9)	6 (9.5)	11 (17.4)
Lower extremity	4 (6.4)	28 (44.4)	32 (50.8)

The following gross morphological attributes were abstracted from the clinical records:

• color
• uniformity of pigmentation
• presence of a raised component on the skin surface
• regular versus irregular shape
• well-defined versus ill-defined borders

Also recorded were the main dermatoscopic features and the diagnoses performed by ELM.

In the context of another study on pigmented lesions still ongoing at our institution, sixteen of our cases of PSCN were also analyzed by a telespectrophotometric system in vivo before surgery. This system, based on measurements of lesion reflectance (i.e., the fraction of light reflected or diffused by a pigmented lesion), provides an objective evaluation of color of skin lesion [19]. The patients underwent to a regular followup for 5 years after surgery.

Results

The size of the lesions ranged from 2mm to 17 mm in diameter, with a median value of 5 mm. The clinical features of the 63 lesions are summarized in Table 2. Lesions were darkly pigmented in nearly all the cases. A uniform dark color was the hallmark of the majority of the lesions. The nevi were very often raised on skin surface, but not a significant number (22.2 %) of these tumors showed a flat conformation. A regular shape was present in 85.7 percent of cases, and a well-defined border was more common than an ill-defined border (87.3 % vs. 12.7 %).

Table 2. Clinical features of 63 pigmented spindle-cell nevi

Feature	Number  (%)	Feature	Number  (%)
Color		Elevation
Black	29  (46.0)	Slightly elevated	44  (69)
Brown	20  (31.7)	Flat	14  (22.2)
Black and brown	9  (14.3)	Nodular	5  (7.9)
Tan	2  (3.2)	Total  63  (100)
Black and blue	1  (1.6)	Shape
Black and grey	1  (1.6)	Regular	54  (85.7)
Brown and red	1  (1.6)	Irregular	9  (14.3)
Total   63  (100)		Total  63  (100)
Uniformity of pigmentation		Borders
Uniform	52  (82.5)	Well-defined	55  (87.3)
Not uniform	11  (17.5)	Ill-defined	8  (12.7)
Total  63  (100)		Total  63  (100)

All cases were also examined by ELM. Table 3 summarizes the clinical diagnoses of whole series of our cases. Table 4 shows clinical and dermatoscopic diagnoses of our 63 lesions.

Figure 1	Figure 2
A dermatoscopic presentation of pigmented spindle-cell nevus showing a prevalence of brown globules forming a rim around the lesion (Fig. 1).
A dermatoscopic presentation of pigmented spindle-cell nevus. The lesion prevalently presents pseudopods arranged regularly at the periphery and retiform depigmentation at the center (Fig. 2).

Figure 3
Telespectrophotometric acquisition is represented, at selected wavelengths (nm) of (a) melanoma; (b) pigmented spindle-cell nevus; (c) compound nevus.

Our data put in evidence the two typical dermatoscopic presentations of PSCN: the first showing a brown to blue pigmentation and a peripheral rim of large brown globules (globular pattern) (Fig. 1), and the second revealing a dark diffused pigmentation and pseudopods regularly distributed at the periphery in a stellate or radiate pattern (starbust pattern) (Fig. 2). The first aspect was present in 34 cases (54 %), the second one in 27 cases (43 %). At ELM examination two lesions showed irregular pigment network and non-homogeneous pigmentationm and were regarded as suspected melanomas.

Figure 4	Figure 5
An atypical pigmented spindle-cell nevus: a small multicolored lesion showing irregular and ill-defined borders. The clinical diagnosis was melanoma in situ (Fig. 4).
A typical pigmented spindle-cell nevus: a small slightly raised dark lesion with defined borders. Melanoma cannot be ruled out on clinical observation (Fig. 5).

All sixteen lesions subjected to telespectrophotometric measurements showed a persistence of their images in the near-infrared band (between 940 and 1,040 nanometers). This datum represents an instrumental confirmation of the dark color of these lesions. This physical behavior of PSCN appears similar to that of melanoma [20]. Figure 3 shows typical reflectance of a melanoma, a PSCN and a common nevus, when imaged at different selected wavelengths. Numerical values of grey levels are proportional to the reflectance. Above 700 nm (near infrared) the common nevus is no longer visible and shows a reflectance close to that of the surrounding normal skin. In contrast, pigmentation of both melanoma and PSCN is detectable up to 1,040 nm.

All patients underwent to a regular followup for 5 years after surgery: no one had local relapse, regional or distant metastases.

Figure 6	Figure 7

Figure 8	Figure 9

Conclusions

After the original description by Reed et al. [4], several series of PSCN have been published and the clinical and the histological features of these lesions have been defined [4, 5, 6, 7, 8, 9, 10, 11]. The data derived from our cases allow an integrated clinical and dermoscopic description of PSCN. The typical tumor is a small slightly raised lesion, generally showing a uniform black or brown color, with regular well-defined borders (Fig. 4). Its dark color makes PSCN a clinical simulator of melanoma. Notably the same tendency of PSCN of having a dark hue at telespectrophotometric analysis is showed by melanoma if examined by this technique [20]. These considerations, not to mention rare cases of lesions showing irregular borders or nonuniform pigmentation (Fig. 5), explain why PSCN is often misinterpreted as melanoma on clinical grounds. Several clinicopathologic studies have reported these difficulties in the clinical diagnosis of PSCN [5, 6, 8, 10]. When clinical diagnoses have been reported, 39-45 percent of PSCN cases had been diagnosed as melanoma [5, 6]. Also 25 percent of our cases had a clinical diagnosis of suspect melanoma (Tables 3 and 4).

Table 3. Clinical diagnosis of 63 cases of pigmented spindle-cell nevus

Diagnosis	Number  (%)
PSCN	38   (60.3)
Suspected melanoma	16   (25.4)
Common nevus	4    (6.3)
Spitz nevus	2    (3.2)
Other	3    (4.8)
Total	63    (100)

Table 4. Clinical and dermatoscopic diagnosis of 63 cases of pigmented spindle cell nevus

Diagnosis	Clinical impression	Dermatoscopic diagnosis
	Number (%)	Number (%)
PSCN	38   (60.3)	61   (96.8)
Melanoma	16   (25.4)	2     (3.2)
Common nevus	4    (6.3)	-        (-)
Spitz nevus	2    (3.2)	-        (-)
Other	3    (4.8)	-        (-)
Total	63    (100)	63    (100)

ELM has provoked a real improvement in the diagnosis of PSCN and Spitz nevus [16, 17]. By this technique we have performed a clearcut diagnosis in the overwhelming majority of PSCN cases. In our series the correct preoperative diagnosis was performed in 61 of 63 cases (97 %). A similar rate of correct diagnosis (93 %) was reached by Pehamberger et al. on a series of 54 cases of pigmented Spitz nevus [17]. However, dermatoscopic features suggesting melanoma are a reality even if rare, as two of our cases show. One of these cases, with a clinical and dermatoscopic diagnosis of melanoma was treated by a major excision with 1-cm margins.

Critical diagnosis and management decisions concerning pigmented lesions should always be based on a combination of clinical and dermatoscopic assessments. Indeed, in rare cases, melanoma can show the characteristics starbust of globular pattern usually seen in PSCN; in these cases, the correct diagnosis must be supported by anamnestic data concerning the history and the evolution of the lesion and by clinical features. This fact once more stresses the importance of not making a diagnosis of a pigmented lesion with ELM alone. In presence of a certain dermatoscopic diagnosis of PSCN on a lesion without a high clinical suspicion for melanoma, our current practice is not to proceed to a surgical excision for histological examination of the lesion; for these cases a careful clinic and dermatoscopic followup of the lesion can be sufficient.

By following this approach, we have reduced the number of diagnostic operations in patients bearing PSCN, sparing many patients unnecessary stress, avoiding complications and conserving medical resources.

Acknowledgments. This research was partially supported by the Italian Association for Cancer Research and the Italian Research Council. We are grateful to Francesca Falcetta and Luisa Morandi for data management. We are grateful to Giovanna Maimone and Claudia Vaccaro for photographic assistance.

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