Dermatology Online Journal

Tubular Apocrine Adenoma in Association with Syringocystadenoma Papilliferum
Fatma Aktepe¹, Yavuz Demir², F. Hüsniye Dilek¹
Dermatology Online Journal 9 (1): 7

1. Department of Pathology, and 2. Department of Plastic and Reconstructive Surgery, Afyon Kocatepe University School of Medicine, Afyon, Turkey. aktepef@hotmail.com

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Abstract

Tubular apocrine adenoma is a very rare sweat gland tumor. In this report, a case of tubular apocrine adenoma in association with syringocystadenoma papilliferum on the scalp is presented. The stroma of the tubular apocrine adenoma consisted of numerous, young fibroblasts with mitotic activity. It was difficult to distinguish stromal cells and epithelial cells from each other in some areas. The characteristics and differences in histopathologic and immunohistochemical findings in these tumors are described.

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Introduction

Tubular apocrine adenoma (TAA), first described in 1972 by Landry & Winkelmann, is a very rare benign sweat gland tumor that appears as a well-defined, deeply located, dermal nodule on the scalp.[1] Fisher described TAA as a minor variant of syringocystadenoma papilliferum (SCAP) but others have suggested that it is an independent clinical entity.[2] TAA may be associated with SCAP and papillary eccrine adenoma (PEA).[2, 3, 4, 5, 6] Histologically, it is difficult to differentiate TAA from PEA in some cases. These tumors, when they demonstrate both eccrine and apocrine differentiation, are referred to as "tubulopapillary hydradenoma". TAA may represent the intermediate phase of the spectrum between SCAP and PEA.

In this report, we present a case of TAA associated with SCAP located on the scalp. The stroma of the TAA consisted of numerous, young fibroblasts with mitotic activity. The differential diagnosis and putative histogenesis based on light microscopical and immunohistochemical findings are discussed in both tumors.

Case Report

Figure 1	Figure 2
Fig. 1. Irregularly branched structures, which are lined by two or more layers of epithelial cells embedded in fibroblastic stroma (H&E, X200).
Fig. 2. Syringocystadenoma papilliferum in the superior part of the lesion and tubular apocrine adenoma in the deeper part (H&E, X40).

Figure 3
Fig. 3. In the upper dermis, papillary projections extend into the dermis. A marked inflammatory infiltrate in the stroma and the papillary stalks is shown (H&E, X100).

A 19-year-old man was admitted to the Plastic and Reconstructive Surgery Clinic with the complaint of a painless nodule on his scalp. The lesion had been present since birth and the size of the lesion had increased in the last several years. Physical examination revealed a pinkish, hairless, verrucous plaque measuring 30X10 mm. The lesion was totally excised.

On microscopic examination, the epidermis showed hyperkeratosis and papillomatosis. A cystic invagination extended downward from the epidermis. Numerous papillary projections, lined by two rows of epithelial cells, protruded into the lumen of the cystic invagination. The peripheral layer consisted of cuboidal or flattened cells and the luminal layer was composed of columnar cells, some of which showed decapitation secretion. The stroma and the papillary stalks of the tumor were densely and diffusely infiltrated with numerous plasma cells (Figure 1). The deeper portion of the tumor consisted of irregularly branched tubular structures with two or more layers of epithelial cells (Figure 2). The luminal cells of the tubules were columnar and showed decapitation secretion, whereas the outer layer was mostly composed of flattened cells. These tubules were surrounded by a fibrous stroma, which consisted of numerous young fibroblasts. Mitosis was observed in some fibroblasts. Tubular structures were admixed with stromal fibroblasts in several areas. Therefore, in these areas it was hard to distinguish the tubular epithelial cells from the stromal cells (Figure 3). These light microscopic findings in the upper level were interpreted as representative of SCAP and those in the deeper level as TAA.

Tumors were stained immunohistochemically for carcinoembryonic antigen (CEA), keratin, S-100, and vimentin. The comparison of the immunoreactivities of the TAA and SCAP are summarized in Table 1.

Table 1. Comparison of the immunohistochemical findings of TAA and SCAP

	Tubular apocrine adenoma		Syringocystadenoma papilliferum
	Luminal cells	Peripheral cells	Luminal cells	Peripheral cells
Keratin	+	+	+	+
CEA	+++(apical)	-	++	++
S-100	-	+	-	-
Vimentin	-	-	-	-

Discussion

The association of TAA with SCAP was first described by Toribio et al. in 1987 in which SCAP was located above TAA.[7] TAA differs from SCAP in several histopathologic findings. SCAP is located in the upper part of the dermis, whereas TAA is located in the deeper part. TAA shows no cystically dilated invaginations extending downward from the epidermis. Papillary projections are absent in TAA. Infiltration of plasma cells is rare or absent in TAA and the stroma of the TAA is composed of dense fibrous connective tissue.[3, 4] However, in our case, tubular structures of the tumor were embedded in a fibroblastic stroma and stromal cells showed several mitotic figures. Stromal cells and epithelial cells could not be easily distinguished from each other in some areas. In this case one could interpret the findings as TAA associated with SCAP or alternatively as SCAP with areas mimicking TAA.

Immunohistochemical findings are shown in Table 1. Both luminal and peripheral epithelial cells of SCAP stained diffusely with antikeratin antibody but staining in the tumor cells of TAA was not diffuse and observed only in some epithelial cells. Immunoreactivity to anti-CEA antibody was seen in the luminal border of tumor cells in TAA, consistent with the findings in previous studies.[3, 4] Anti-CEA immunoreactivity in the tumor cell cytoplasm of SCAP was faint. S-100 protein was detected in the peripheral layer of tumor cells of the TAA, as Ishiko et al. have reported.[4] Ishiko suggested that S-100 staining cells might be myoepithelial cells.[4] S-100 staining was not observed in the tumor cells of SCAP in the present case. On the basis of our findings, we believe that SCAP and TAA are either different tumors or different phases in the development of tumor.

The histogenesis of the SCAP is unclear. While some authors have suggested that SCAP originates from eccrine elements,[3, 9] others have stated that these tumors originate from apocrine elements.[8] In recent studies, these tumors were suggested to arise from either pleuripotential appendageal cells or apo-eccrine glands.[8, 9] Apocrine differentiation has been demonstrated in TAA by light microscopy, enzyme histochemistry, and electron microscopy.[1, 2, 8, 10] Contrary to these findings, both eccrine and apocrine differentiation have also been shown to exist in TAA.[5, 6] The term "tubulopapillary hidradenoma" has been proposed for cases where eccrine and apocrine differentiation are both observed, and in these tumours TAA was believed to be associated with PEA.[5, 6] Histomorphologic features of TAA, PEA, and SCAP show many similarities and have minor differences. TAA may have a connection to the overlying epidermis by dilated ducts as in SCAP.[4] Both TAA and PEA exhibit mainly tubular structures, which may show eccrine or apocrine differentiation.[1, 7, 10, 11] Regarding the previous findings and suggestions, it may be proposed that these tumors might develop from pleuropotential appendageal cells. Therefore, TAA may be an intermediate phase between SCAP and PEA in tumorogenesis.

We believe that further comparative studies with light microscopical, immunohistochemical, and electron microscopical findings, are needed to clarify the histogenesis of these tumors.

References

1. Landry M, Winkelmann RK, An unusual tubular apocrine adenoma: histochemical and ultrasructural study. Arch Dermatol 1972;105:869-876.

2. Fisher TL. Tubular apocrine adenoma (Letter to editor). Arch Dermatol 1973;107:137.

3. Ansai S, Watanabe S, Aso K. A case of tubular apocrine adenoma with syringocystadenoma papilliferum. J Cutan Pathol 1989;16:230-236.

4. Ishiko A, Shimizu H, Inamoto N, Nakmura K. Is tubular apocrine adenoma a distinct clinical entity? Am F Dermatopathol 1993;15:482-487.

5. Fox SB, Cotton DWK. Tubular apocrine adenoma and papillary eccrine adenoma: entities or unity? Am J Dermatopathol 1992;14:149-154.

6. Tellechea O, Reis JP, Marques C, Baptista AP. Tubular apocrine adenoma with eccrine and apocrine immunophenotypes or papillary tubular adenoma? Am J Dermatopathol 1995;17:499-505.

7. Toribio J, Zulaica A, Peterio C. Tubular apocrine adenoma. J Cutan Pathol 1987;14:114-117.

8. Elder D, Tumours of epidermal appendages. Elenitsas R, Ragsdale BD. In Lever¹s Histopathology of the Skin. 8th ed. Philadelphia; JB Lippincott. 771-786, 1997

9. Mammino JJ, Vidmar DA. Syringocystadenoma papilliferum. Int J Dermatol 1991;30:763-766.

10. Barnadas MA, Moreno A, Pujol R, et al. Tubular apocrine adenoma. Description of 4 cases. Med Cutan Ibero Lat Am 1990;18:35-39.

11. Ambo M, Kumariki M, Kobayashi, Ohkawara A. Papillary eccrine adenoma with pomegranate-like appearance. J Dermatol 1997;24: 773-776.

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