Basaloid follicular hamartoma: A case report and review of the literature

Multiple follicular abnormalities in a 1-year old cat consistent with basaloid follicular hamartomas

BACKGROUND

In humans, basaloid follicular hamartomas are benign follicular tumours, that can be solitary or multiple, in which case they show autosomal dominant inheritance.

HYPOTHESIS/OBJECTIVES

This study describes clinical and histopathological findings observed in a young cat, which could be consistent with basaloid follicular hamartomas.

CASE DESCRIPTION

Multiple follicular abnormalities, consistent with cutaneous diffuse basaloid follicular hamartomas, were observed in skin samples from a one-year old neutered domestic short hair cat. Clinical signs were diffuse symmetrical alopecia with exaggerated skin markings (ventral abdomen, thorax and medial aspects of the limbs) and intense follicular-centred thickening (face and feet). Microscopic lesions were characterised by multiple proliferative follicular abnormalities in all samples. The epidermis showed a very irregular surface with the follicles filled with variably pigmented keratin. The epithelial walls of the follicles had multiple small hyperplastic basaloid cells foci. In the superficial dermis under the epidermis and around the follicles, fibroblastic spindle-shaped mesenchymal cells with a homogeneous moderate density were present in the collagenous connective tissue. The interfollicular epidermis was also abnormal with multiple small proliferating trichoblastic foci originating from the basal layer. RNAscope testing for feline papillomavirus was negative.

CONCLUSIONS AND CLINICAL RELEVANCE

This case report provides the first evidence of clinical and histopathological findings of multiple follicular abnormalities, consistent with cutaneous diffuse basaloid follicular hamartomas in a cat.

Basaloid tumors arising from seborrheic keratosis: Malignant basal cell carcinoma or benign basaloid follicular hamartomatous proliferation?

BACKGROUND

Basaloid tumors arising from seborrheic keratosis (SK) that resembled basal cell carcinoma (BCC) were infrequently observed in our patients. They also exhibited morphologic features similar to those of trichoblastoma or basaloid follicular hamartoma.

METHODS

We retrospectively collected cases of SK with basaloid tumors from 2001 to 2017. Ten cases of BCC, five of nevus sebaceus with trichoblastoma, five of trichoblastoma, and five of trichoepithelioma were included as controls. Tumor-associated antigens Bcl-2, CD10, PHLDA1, and CK20 were tested. Antigenic markers CD34 and CD10 were used to analyze peritumoral stroma features and Ki-67 and pHH3 to measure the mitotic activity.

RESULTS

Ten cases of SK with basaloid tumors were found and all located in non-sun-exposed areas, including five men and five women, with a mean age of 61 years. A distinct PHLDA1 staining was not observed. The staining patterns of basaloid tumor lobules associated with SK were similar to the benign control group. Bcl-2 staining in the tumor lobules was mostly negative. Peritumoral CD10 stain and CK20-positive Merkel cells in the lobules were observed and the mitotic counts were low.

CONCLUSION

Basaloid tumors arising from SK are not always BCC. They were all benign follicular hamartomatous proliferation in this case series.

Hamartomas of skin and soft tissue

Hamartomas are benign lesions composed of aberrant disorganized growth of mature tissues. Choristomas are similar, except that they are composed of tissues not normally found at the anatomic site in which the lesion is arising. A wide range of hamartomas and choristomas can arise in the skin and soft tissue. Some of these may cause diagnostic difficulty and potentially be mistaken for neoplasms. Some neoplasms may resemble hamaratomas. Here we review the current clinical and pathologic features of these lesions, both common and rare, and discuss how to distinguish them from other entities in the differential diagnosis.

Linear Unilateral Basaloid Follicular Hamartoma Following Blaschko's Lines: Two Case Reports and Review of the Literature

Basaloid follicular hamartoma (BFH) is a rare follicular malformation characterized by variable clinical presentations and identical histopathologic features. We present the cases of a 3-month-old boy and an 8-year-old boy with linear unilateral BFH. To the best of our knowledge, only 14 cases of linear unilateral BFH have been described in the English-language literature.

Unilateral segmentally arranged basaloid follicular hamartomas with osteoma cutis and hypodontia: a case of Happle-Tinschert syndrome

Happle-Tinschert syndrome (HTS) is a rare syndrome characterized by segmentally arranged basaloid follicular hamartomas (BFH) associated with ipsilateral osseous, dental and cerebral abnormalities. Happle and Tinschert first reported this disorder in 2008, and three cases with similar presentations have since been reported. We report another case, that of a 40-year-old man, presenting with the characteristic clinical features of HTS.