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Ninety-six proliferating cutaneous epithelial cysts were classified into two subtypes, proliferating trichilemmal cysts (PTC) and proliferating epidermoid cysts (PEC), depending on the mode of keratinization or the origin of the tumors. The clinicopathological features and the biological behavior of these two subtypes were compared. Among 63 patients with PTC, 45 (71%) were women and 18 (29%) were men. The most common site was the scalp (78%), followed by the trunk (13%). These tumors were well circumscribed subepidermal lesions and demonstrated uniform histologic pattern with varying degrees of cytologic atypia. A few tumors extended into the epidermis and occasionally became ulcerated. Follow-up of 59 (94%) PTC for an average of 4 years revealed recurrence in one. Ten tumors demonstrated carcinomatous changes including one with anaplastic carcinoma and regional lymph node metastasis. None of these tumors recurred or developed further metastasis following wide excision. Of 33 PECs, 12 (36%) occurred in women and 21 (64%) in men. These tumors were widely distributed in the pelvic and anogenital areas (36%), followed by the scalp (21%), upper extremities (18%), and trunk (15%). Seventy-nine percent of the PECs were located in areas outside the scalp. The PECs were subepidermal tumors but often communicated to the surface. The histologic pattern of PEC was more variable than that of PTC. Seven tumors exhibited carcinomatous changes. Follow-up of 30 (91%) PEC revealed local recurrences in 6, with multiple recurrences in 3, and extensive local invasion in 2, resulting in death in one. Greater anaplasia, high mitotic rate and deeper invasion were associated with increased incidence of recurrence and aggressive behavior. Although both PTC and PEC were locally aggressive tumors and potentially malignant, distant metastasis was unusual. These tumors should be treated with wide local excision, especially those showing cytologic atypia and carcinomatous changes.

The cutaneous deposition disorders are a group of unrelated conditions characterized by the presence of either endogenous or exogenous substances within the dermis or the subcutis. Part I of this two-part series will focus on metabolic processes involved in the endogenous deposition in the various forms of amyloidosis, porphyria, colloid milium, and lipoid proteinosis. We will also review the clinical, histologic, biochemical, and ultrastructural findings relevant to each disorder. Basic mechanisms of pathogenesis, diagnostic modalities, and treatment options are also discussed.

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We report 14 cases of trichogerminoma, a rare form of cutaneous adnexal neoplasm, derived from hair germ epithelium. The neoplasms occurred in 9 men and 5 women. Their ages ranged from 16 to 73 years (median 53 years). The tumors were slow growing, asymptomatic dermal or subcutaneous nodules, located on the head and neck (6), trunk (4), extremities (2) and hip (1), with no distinguishing clinical features. Histologically, trichogerminomas were characterized by sharply circumscribed, pseudoencapsulated dermal and subcutaneous nodules, ranging in size from 0.4 to 4.0 cm in diameter (mean 1.9 cm). The nodules were subdivided into lobules separated by variable amounts of stroma that demonstrated varying cellularity and mucin content. The lobules were composed of basaloid cells that formed densely packed, round nests or "cell balls" resembling hair bulbs. The basaloid cells demonstrated peripheral palisading, keratinization and differentiation towards various pilosebaceous structures. Retraction spaces, well developed hair follicles and hair shafts were not observed. These distinctive histologic features separated these neoplasms from other tumors of pilar origin and from basal cell carcinoma. The trichogerminomas behaved in a benign fashion with one exception. Complete excision of the lesions is the treatment of choice.