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Background Cysts are very common in the routine of dermatopathology but follicular germinative (trichoblastic) differentiation in cysts is seen rarely. The presence of follicular germinative differentiation in a cyst alerts to consider the possibility of a basal cell carcinoma (BCC) arising in a cyst. Methods Five cystic lesions with zones of follicular germinative differentiation were collected. Hematoxylin and eosin sections were reassessed for architecture, types of follicular differentiation and stromal characteristics; immunohistochemical studies with Ber-EP4 were analyzed. Articles about follicular germinative differentiation in cystic lesions were reviewed. Results Cystic lesions with follicular germinative differentiation have been described in the literature under various names including trichoblastic infundibular cyst, cystic trichoblastoma, cystic panfolliculoma (CPF), dermoid cyst with basaloid proliferations, folliculosebaceous cystic hamartoma and BCC occurring in infundibular cysts. The lesions presented by us could be classified as three cystic trichoblastomas, one CPF and one cystic hamartoma with follicular germinative differentiation. Conclusions Histopathologically, cystic trichoblastomas can be separated from CPFs. Some lesions defy classification and may be regarded as cystic follicular hamartomas. The presence of follicular papillae and bulb-like structures, advanced follicular differentiation like that of inner and outer root sheath exclude the differential diagnosis of BCC arising in a cyst.

Folliculosebaceous cystic hamartoma (FCH) is a relatively rare and recently described lesion of the skin. Mostly, it involves the skin of the head and neck area. It is considered by most authors as a form of non-neoplastic cutaneous hamartoma comprising follicular, sebaceous and stromal elements. However, few regard it as a sebaceous trichofolliculoma, i.e. a variant of trichofolliculoma. FCH of the nipple of female breast is a very rare lesion with only one previous case reported so far in the literature. We report a similar case with a brief review of the literature.

Background Folliculo-sebaceous cystic hamartoma (FSCH) is an uncommon skin condition presenting as a slow-growing papulo-nodular lesion, in or around the nose. Most cases are not clinically suspected and only histopathological examination allows the diagnosis. Pathological features include a dermal-located infundibulo-cystic structure with sebaceous glands radiating around, a stromal component encircling the epithelial structures, with clefts between the lesional epithelial and stromal parts, as well as between this and the adjacent dermis. Results We report eight patients with the diagnosis of FSCH (5 females and 3 males), with ages ranging from 35 to 77 years. Most cases (5 out of 8) were located in or around the nose and sizes were comprised between 0.6 and 1.2 cm. Lesions had grown for long periods of time, up to ten years in one case. Immunohistochemistry showed staining for p63 in the epithelial component of all lesions, while CD10 was only present in some sebocytes. CD34 and Factor XIIIa positive cells were present in the lesional stroma. Staining for androgen and alpha-estrogen receptors was also usually noticed. Conclusions FCSH is a hamartomatous skin lesion, clinically indistinct but with well-defined histopathological features. Immunohistochemistry shows a profile very close to normal sebaceous glands. © 2008 Blackwell Munksgaard.

Background: Folliculosebaceous cystic hamartoma (FSCH) is a rare cutaneous hamartoma consisting of dilated folliculosebaceous units invested in mesenchymal elements. These lesions have a striking predilection for the central face and scalp of adults. The vast majority of lesions present as 0.5–1.5-cm papules or exophytic nodules. A single case of giant FSCH has been reported on the upper back. Methods: A 32-year-old woman presented with a (15 cm in greatest dimension) plaque-like, multinodular lesion on her left upper arm for several years. The lesion was clinically suspected to be a nevus sebaceus. Results: The skin excision showed numerous dermal and subcutaneous dilated follicular structures with peripherally radiating sebaceous lobules, hair follicles, and surrounding mesenchymal elements consistent with FSCH. Conclusion: To our knowledge, this is the second case of giant FSCH. Our case is unique for its larger size, more plaque-like growth, and location on an extremity when compared to the seminal case of giant FSCH.

Folliculo-sebaceous cystic hamartoma (FCH) was described as an entity recently and was defined as an adnexal hamartoma, showing above all an infundibular cystic structure linked to many sebaceous lobules. Differentiation toward the inferior segment of the hair follicle also occurs, although to a markedly lesser degree. Signs of regression and rest corresponding to the normal follicular cycle are often apparent in these follicular proliferations. Therefore so-called FCH has much in common with the newly described late stage of trichofolliculoma, which also exhibits an infundibular cyst and sebaceous and follicular differentiation with various signs of catagen and telogen. Comparing our 8 cases of FCH and 31 cases of trichofolliculoma, we came to the conclusion that FCH is the very late stage of trichofolliculoma. This stage could be characterized by a nearly complete regression of the transient follicular epithelium, whereas concurrent growth and maturation of sebaceous elements appear.

The trichofolliculoma is a follicularly differentiated hamartoma, usually described as showing many vellus follicles, spreading from a central infundibular cyst. In spite of the well known regressive changes of normal hair follicles during catagen and telogen, the possibility of corresponding changes in the trichofolliculoma has not yet been discussed in the literature. By examining a total of 31 cases of trichofolliculoma it is demonstrated that this hamartoma undergoes an evolutionary process with great morphological changes, which can be attributed to the anagen, catagen, and telogen phase of the follicular cycle.

We present a case of follicular cystic hamartoma, a distinctive cutaneous malformation characterized by marked overgrowth of folliculosebaceous units accompanied by appreciable mesenchymal alterations, including fibroplasia, increased vascular components, and numerous adipocytes. A conspicuous feature of our case is an aggregation of thick trespassing nerve bundles in the deep portion of the neoplasm. An immunohistochemical study revealed the nerve bundles were immunoreactive for the general neuronal marker protein gene product 9.5. The nerves, however, stained negatively with antibodies against neuropeptides such as calcitonin gene-related peptide, substance P, vasoactive intestinal polypeptide, and neuropeptide Y, all of which are known to be contained in normal cutaneous nerves. The presence of these aberrant nerve bundles devoid of the normal expression of neuropeptides supports the concept that folliculosebaceous cystic hamartoma is a true, tumor-like malformation characterized by abnormal overgrowth of normal components of the skin.

Folliculosebaceous cystic hamartoma (FSCH) is a rare, recently recognized cutaneous hamartoma comprised of follicular, sebaceous and mesenchymal elements. Fewer than 30 cases have been reported to date. The authors present two additional cases of FSCH.