During the past 2 decades, the use of transverse sections in the evaluation of scalp biopsy specimens has led to a better understanding of the histopathologic changes in both cicatricial and noncicatricial alopecia. However, the technique has provided the most significant gains in the study of the latter type of alopecia, where evaluation of follicle density and follicular dynamics are integral to accurate diagnosis. This report reviews the histopathologic findings of four common types of noncicatricial alopecia: androgenetic alopecia, telogen effluvium, alopecia areata, and trichotillomania/chronic traction alopecia.

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Renal cell carcinomas (RCCs) are rare in the pediatric population; when they occur, a significant percentage are associated with specific cytogenetic abnormalities and germline mutations. These include mutations in the von Hippel-Lindau ( VHL) gene and translocations involving the TFE3 transcription factor gene on Xp11.2. Here we report a case of a 3-year-old child with a large renal mass. Histologic examination of the tumor showed a predominantly nested growth pattern with some papillary foci. Cytogenetic analysis revealed a karyotype of t(X;1)(p11.2; p34.3), consistent with a TFE3-associated RCC. Interestingly, sequencing of the patient's VHL gene revealed a single point mutation, previously seen in a subgroup of patients with von Hippel-Lindau disease. This is the first reported case, to our knowledge, of t(X;1)-associated RCC in a patient with concurrent VHL gene mutation.

An 8‐year‐old male presented with several 1–4 cm, indurated, brownish‐red nodules with superficial, punctate hemorrhagic crusts localized to the groin, which developed over several weeks. An initial biopsy was consistent with Langerhans cell histiocytosis. A work up, including a chest and abdominal CT scan demonstrated a large mediastinal mass which was diagnosed as precursor T cell lymphoblastic lymphoma. Treatment with a chemotherapeutic protocol resulted in shrinkage of both the mediastinal and cutaneous lesions. Late in the course of treatment the cutaneous lesions rapidly recurred and spread to various sites. A second skin biopsy showed an extensive diffuse infiltrate of histiocytic‐appearing cells extending from the papillary dermis into the superficial subcutis. The cells had markedly pleomorphic, vesicular nuclei and abundant amphophilic cytoplasm. Numerous mitotic figures were present. The neoplastic cells were S‐100 protein and CD1a positive by immunohistochemistry. The histopathologic diagnosis was Langerhans cell sarcoma. Gene rearrangement studies demonstrated clonal rearrangement of the T cell receptor gamma gene in specimens from both the mediastinal mass and one of the recurrent cutaneous lesions. The sizes of the PCR products were identical demonstrating a clonal relationship between the two neoplasms.