Malignant proliferating trichilemmal tumour

Malignant proliferative ependymoma of the neck with lymph node metastasis: A case report

BACKGROUND

Malignant proliferating trichilemmal tumor (MPTT) is an infrequent malignant neoplasm originating from cutaneous appendages, with only a handful of documented cases. This report delineates a unique instance of MPTT situated in the neck, accompanied by lymph node metastasis. A comprehensive exposition of its clinical trajectory and imaging manifestation is presented, aiming to enhance comprehension and management of this atypical ailment.

CASE SUMMARY

Patient concerns: A 79-year-old male presented with a longstanding right neck mass persisting for over six decades, exhibiting recent enlargement over the past year. Diagnoses: Enhanced magnetic resonance imaging of the neck unveiled an elliptical mass on the right neck side, characterized by an ill-defined border and a heterogeneous signal pattern. The mass exhibited subdued signal intensity on T1-weighted imaging (T1WI) and a heterogeneous high signal on T2-weighted imaging (T2WI), interspersed with a lengthy T1 and T2 cystic signal motif. Close anatomical association with the submandibular gland joint was noted, and intravenous gadolinium diethylene triamine pentaacetic acid administration facilitated conspicuous enhancement. Substantial enhancement of the solid segment prompted an initial preoperative diagnosis of malignant nerve sheath tumor. However, post-surgery histopathological and immunohistochemical analysis conclusively confirmed the diagnosis as malignant hyperplastic external hair root sheath tumor. Intervention: Complete excision of the tumor was successfully executed. Outcomes: The patient experienced a favorable postoperative recovery.

CONCLUSION

Malignant proliferative trichilemmal tumor external hair root sheath tumor is a cystic-solid lesion, appearing as low signal on T1WI images or high signal on T2WI with enhancement of the solid component. Suspicions of malignancy are heightened when the tumor border is indistinct, tissue planes are breached, or when linear or patchy high signals are observed in the subcutaneous tissue on T1 liver acquisition with volume acceleration enhanced images along with intermediate signal on T2WI and restricted diffusion on diffusion-weighted imaging images. Strong consideration for malignancy should arise if there are signs of compromised adjacent tissue relationships or direct invasion evident on imaging. We have incorporated the above-mentioned content into the entire manuscript.

Malignant Proliferating Pilar Tumor: Clinicopathologic, Immunohistochemical, and Molecular Study of 17 Cases

Proliferating pilar tumors are rare neoplasms that differentiate toward the outer sheath near the isthmus and can rarely undergo malignant transformation. We performed histopathologic evaluation on 26 benign proliferating pilar tumor (BPPT) and 17 malignant proliferating pilar tumor (MPPT). Ki-67 and p53 immunostains were performed on 13 BPPT and 10 MPPT. Six MPPT cases were successfully analyzed by a next-generation sequencing platform which surveyed exonic DNA sequences of 447 cancer genes and 191 regions across 60 genes for rearrangement detection. Patient demographics and clinical characteristics were similar between the BPPT and MPPT groups. Follow-up data of 16 of 17 MPPT (median, 25 mo) showed metastasis in 1 MPPT. The histologic features associated with MPPT include size >2.5 cm, adjacent desmoplastic stroma, small nests or cords of atypical epithelium in surrounding stroma, irregular infiltration or borders, abnormal keratinization, large hyperchromatic nuclei, prominent nucleoli, severe cytologic atypia, nuclear pleomorphism, necrosis, and increased mitotic figures. MPPT harbors copy number gains of 15q and losses of 6p and 6q, findings previously reported in BPPT. However, MPPT harbors frequent TP53 mutations as molecular markers of progression. Different from cutaneous squamous cell carcinoma, MPPT more frequently demonstrates low tumor mutational burden and typically lacks a UV signature, suggestive of a different etiologic pathway than squamous cell carcinoma. In summary, with a median follow-up of 25 months, this study shows that MPPT is a biologically indolent carcinoma with rare metastasis. Molecular analyses suggest a non-UV-related pathogenesis with frequent TP53 aberration.

Proliferating Pilar Tumors Are Characterized by Recurrent 15q, 6q, and 6p22.2 Alterations

ABSTRACT

Proliferating pilar tumors (PPTs) are rare neoplasms of external root sheath derivation, which most commonly occur on the scalp of elderly women. Although typically showing classic histologic features such as trichilemmal type keratinization, a lobular architecture and peripheral palisading, squamous cell carcinoma (SCC) remains a common diagnostic pitfall. Therefore, we sought to explore the molecular pathogenesis of PPTs and compare it with that of cutaneous squamous cell carcinoma (cSCC). Herein, we describe the use of a next-generation DNA sequencing platform to provide the most comprehensive molecular genetic analysis to date of a cohort of 5 PPTs and compare them to 5 head and neck cutaneous SCCs. Recurrent broad arm-level gains of 15q and concurrent single-copy losses of 6q and 6p22.2 were observed in 4 of 5 (80%) PPT cases. Other recurrent mutations or alterations of significance were not found in PPTs. Notably, these chromosomal changes were not identified in any of the 5 cutaneous SCCs, which instead showed recurrent alterations in the known SCC driver genes TP53 , CDKN2A , and NOTCH1 . Here, we show for the first time that PPTs are molecularly distinct from cutaneous SCC and provide evidence that recurrent alterations in chromosome 15 and chromosome 6 are central to the pathogenesis of PPTs.

A rare ossifying trichilemmal cyst in a young female patient: Case report and literature review

Trichilemmal cysts constitute the second most common cutaneous cysts and are mostly presented on the scalp of middle aged women. It is, therefore, unusual for a young person to have a trichilemmal cyst and it is extremely rare for a trichilemmal cyst to be ossified. In literature, only 8 cases of trichilemmal cysts with concomitant ossification have been described. We report the case of a 22 year old female who presented with a scalp nodule and was treated via surgical excision of the lesion. The pathology examination of the surgical specimen revealed a lesion consisting of a multilayered squamous epithelium of slightly eosinophilic maturing keratinocytes. There was no granular layer, whereas the core of the lesion was occupied by mature bone tissue with calcium deposits. The definite diagnosis of the pathology report was ossifying trichilemmal cyst. The aim of this report is, to enlighten clinicians about this rare pathological entity.

TP53 Abnormalities and MMR Preservation in 5 Cases of Proliferating Trichilemmal Tumours

Proliferating trichilemmal tumours (PTT) are defined by a benign squamous cell proliferation inside a trichilemmal cystic (TC) cavity. A possible explanation of this proliferative phenomenon within the cyst may be molecular alterations in genes associated to cell proliferation, which can be induced by ultraviolet radiation. Among other genes, alterations on TP53 and DNA mismatch repair proteins (MMR) may be involved in the cellular proliferation observed in PTT. Based on this assumption, but also taking into account the close relationship between the sebaceous ducts and the external root sheath where TC develop, a MMR, a p53 expression assessment and a TP53 study were performed in a series of 5 PTT cases, including a giant one. We failed to demonstrate a MMR disorder on studied PTT, but we agree with previous results suggesting increased p53 expression in these tumours, particularly in proliferative areas. TP53 alteration was confirmed with FISH technique, demonstrating TP53 deletion in most cells.