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Malignant Proliferating Trichilemmal Tumor

1997; Lippincott Williams & Wilkins; Volume: 19; Issue: 2 Linguagem: Inglês

10.1097/00000372-199704000-00017

1533-0311

Giuseppe Noto, G Pravatà, Mario Aricò,

Tumors and Oncological Cases

To the Editor: Proliferating trichilemmal tumor (PTT) is an uncommon appendageal skin neoplasm that, in very rare instances, may metastasize. In 1989, we reported a patient with a well-differentiated, malignant PTT who had developed lymph node metastases (1). We are now updating this case and providing a review of the literature on malignant and metastasizing PTT. In March 1982, a 42-year-old woman presented at our institution with a red nodule in the occipital region. After the nodule was excised, histologic examination showed PTT; therefore, a larger excision was performed. Six months later, there was some recurrence, and a new excision showed PTT features. In May 1985, the patient presented with a new local relapse of a tumor measuring 3 cm in diameter. Four months later, enlarged lymph nodes on the left side of the neck were also excised. Histological work showed nodal metastases of PTT. In December 1986, there was another local recurrence, so a new surgical intervention was performed. Over the following years she had some further local relapses, for a total, including the previous ones, of eight surgical excisions accompanied by radiotherapy. In 1992, following infiltration of the occipital periostium due to a relapse involving the cervical area at C1 level, a surgical intervention was carried out with wider demolition and replacement with a muscular-skin flap taken from the late dorsal muscle. No further distant metastases developed. After some cycles of chemotherapy with cys-platinum, alpha-interferon and vinorelbine, the patient died in August 1995 following locoregional extension of the tumor into the cervical area. PTT undergoes outer root sheath differentiation and exhibits a compact, abrupt tricholemmal keratinization without granular layer interposition (Fig. 1). PTT shares this kind of keratinization with the tricholemmal cyst: the outer root sheath is at the level of the isthmus where the inner root sheath disappears and the infundibular sac is in the catagen and telogen hairs. PTT may also include matrical structures with a pattern similar to that seen in squamous carcinomas with pilar differentiation (2,3). PTT usually appears clinically as a firm nodule on the scalp of elderly women. Histological examination shows a dermal lobular proliferation of squamous epithelium, in some areas constituted by clear cell containing glycogen, circumscribed by a glassy and fairly cellular stroma. These lobes exhibit tricholemmal keratinization with occasional calcification, usually in the central area. Within the squamous proliferation, one can observe dyskeratotic cells, shadow cells, and mitosis, as well as a palisading arrangement of the nuclei at the periphery of the lobes (1,2).FIG. 1: Abrupt, compact trichilemmal keratinization in the central area of a lobular epithelial proliferation. (H&E)To the best of our knowledge, to date 18 cases of malignant PTT have been reported in detail (1,4-14). Metastases are very rare (Fig. 2). Table 1 summarizes the data for 11 cases of malignant PTT with metastases (1,4-10,14). Seven cases arose in the scalp, two in the head (i.e., ear and cheek, respectively) one in the arm, and one in the inguinal region. All but two cases had metastases in the locoregional lymphnodes. The inguinal case had lung, liver, and mediastinum metastases, and the case that started in the cheek area (5) underwent a generalized dissemination.FIG. 2: A lymph node metastasis reproducing trichilemmal keratinization. (H&E)TABLE 1: Metastasizing malignant proliferating trichilemmal tumors reported in detail in the literature Differential diagnosis between benign and malignant PTT can be made on the basis of mitotic rate, cytological and architectural atypia, necrosis, and stromal infiltration (12,15). In some cases, atypical areas were admixed with well-differentiated areas (12,14). However, cases with little or no cytologic and architectural atypia may exhibit aggressive behavior and vice-versa (1,7,13). A morphometric analysis of PTT found no critical differences between benign and malignant PTT; instead the cell population was homogeneous in each sample, suggesting that the biological behavior of PTT is not related to its histologic appearance (16). When ploidy was studied in PTT (13,15), nondiploid cells were found in malignant as well as histologically benign PTT, and the proliferation index was increased in nondiploid cases (15). Our patient died as a result of locoregional extension of her tumor, not distant or regional metastases. In our opinion, PTT should be considered a low-grade carcinoma; nevertheless, accurate follow-up is recommended in all cases, since its biological behavior seems to be histologically unpredictable. Giuseppe Noto, M.D. Gabriella Pravatà, M.D. Mario Aricò, M.D. Department of Dermatology; University of Palermo; Palermo, Italy