A perineal fluid-filled structure was discovered in a 6-year-old intact female Irish water spaniel suffering from intermittent constipation. Diagnostic tests revealed the structure was immediately caudal to the vagina and compatible with a cyst. Surgical excision was required for resolution of clinical signs. Histology confirmed the structure was a cyst. The exact origin is unknown; however, the variety of lining epithelia, including sections with mucin production, and a well-differentiated smooth muscle layer, were most consistent with development from the lower hindgut or urogenital sinus during embryonic growth. The histologic and anatomical similarities with human retrorectal cystic hamartomas were key in establishing the diagnosis of a perineal cystic hamartoma. Following removal, constipation resolved, and the cyst did not recur.

Curry-Jones syndrome (CJS) is a pattern of malformation that includes craniosynostosis, pre-axial polysyndactyly, agenesis of the corpus callosum, cutaneous and gastrointestinal abnormalities. A recurrent, mosaic mutation of SMO (c.1234 C>T; p.Leu412Phe) causes CJS. This report describes the gastrointestinal and surgical findings in a baby with CJS who presented with abdominal obstruction and reviews the spectrum of gastrointestinal malformations in this rare disorder. A 41-week, 4,165 g, female presented with craniosynostosis, pre-axial polysyndactyly, and cutaneous findings consistent with a clinical diagnosis of CJS. The infant developed abdominal distension beginning on the second day of life. Surgical exploration revealed an intestinal malrotation for which she underwent a Ladd procedure. Multiple small nodules were found on the surface of the small and large bowel in addition to an apparent intestinal duplication that seemed to originate posterior to the pancreas. Histopathology of serosal nodules revealed bundles of smooth muscle with associated ganglion cells. Molecular analysis demonstrated the SMO c.1234 C>T mutation in varying amounts in affected skin (up to 35%) and intestinal hamartoma (26%). Gastrointestinal features including structural malformations, motility disorders, and upper GI bleeding are major causes of morbidity in CJS. Smooth muscle hamartomas are a recognized feature of children with CJS typically presenting with abdominal obstruction requiring surgical intervention. A somatic mutation in SMO likely accounts for the structural malformations and predisposition to form bowel hamartomas and myofibromas. The mutation burden in the involved tissues likely accounts for the variable manifestations.

Fibrous hamartoma of infancy (FHI) is a rare benign soft tissue tumor with a triphasic organoid histologic appearance. The authors present a case of a 21-month-old healthy girl with a slowly growing flesh-colored subcutaneous plaque 12cm in size on the lower back, with overlying hypertrichosis. A punch biopsy revealed a proliferation of spindle cells infiltrating the dermis and hypodermis organized in a dense storiform pattern with a strong diffuse positivity for CD34. The diagnosis of congenital dermatofibrosarcoma protuberans (DFSP) was considered and an excision was performed. Histopathologic analysis showed an extensive poorly demarcated mass infiltrating the dermis and hypodermis, composed of different components: a monomorphous fibroblastic/myofibroblastic component, a mature adipose component, and an immature mesenchymal basophilic component. The clinical aspects with the histologic and immunohistochemical features led to the diagnosis of giant fibrous hamartoma of infancy. In our case the strong diffuse CD34 positivity was a diagnostic pitfall leading to an incorrect hypothesis of congenital DFSP. The characteristic triphasic histology of FHI was missed owing to the small size of the punch biopsy. This article highlights the importance of being aware of the CD34+ dermal mesenchymal tumor differential diagnosis and the necessity of appropriate size biopsies to avoid sampling error.

Folliculosebaceous cystic hamartoma (FSCH) is a benign lesion that presents as a solitary papule or nodule that typically affects the face and scalp of adults. A few reports have observed a congenital presentation. We present an infant boy exhibiting a tumor with overlap features between an FSCH and fibrofolliculoma in the perianal region that was first noticed at 6 months of age. The histological examination showed a hamartomatous benign proliferation of hair follicles and disordered sebaceous glands, which is consistent with the infundibular structures and radiating sebaceous glands that are typically observed in previously reported cases of FSCH. Sebaceous differentiation is a hallmark feature of FSCH. Folliculosebaceous cystic hamartoma is believed to be a late-stage form of trichofolliculoma (TF). Another consideration is that FSCH and TF are two distinct entities set apart by their degree of sebaceous or follicular differentiation and development of the mesenchymal stroma.

Fibrous hamartoma of infancy (FHI) is a rare, benign soft tissue lesion observed in infants characterized histologically by triphasic appearance of bland fibroblastic fascicles, mature adipose tissue, and nodules of primitive myxoid mesenchyme. Preoperative and intraoperative recognition of FHI presents a significant diagnostic challenge due to nonspecific imaging findings and its histologic similarities to alternate benign and malignant entities. Management requires complete local excision and clinical follow-up to monitor for recurrence. Here, we present the diagnosis, management, and two-year follow-up of a 13-month-old boy with a scrotal FHI in addition to a comprehensive literature review of this entity.

Fibrous hamartoma of infancy (FHI) is a benign mesenchymal tumor of young children. It has a broad clinical differential diagnosis and is often clinically confused for vascular and malignant soft tissue neoplasms. Recognition of the unique histologic features of FHI, a triphasic population of mature adipose tissue, mature fibrous tissue, and immature mesenchymal tissue, will ensure the correct diagnosis. In this report we present a case of this rare entity, including the associated clinical, radiologic, and histologic findings.

Glomus tumor is a rare benign vascular hamartoma derived from the modified smooth muscle cells of the glomus body. Paroxysmal pain is the leading symptom. A 78-year-old woman presented at our clinic with a 50-year history of a slow growing painful purple blue tender nodule under the right fourth finger nail. Dermoscopy and magnetic ressonance confirmed the presence of a large subungual tumor and total surgical excision was performed after partial nail plate avulsion. Histologic examination confirmed a glomus tumor. After 1 year of follow-up, the nail grew with normal shape and neither complications nor recurrence were observed.