DICER1 tumor predisposition syndrome: an evolving story initiated with the pleuropulmonary blastoma

DICER1 syndrome (OMIM 606241, 601200) is a rare autosomal dominant familial tumor predisposition disorder with a heterozygous DICER1 germline mutation. The most common tumor seen clinically is the pleuropulmonary blastoma (PPB), a lung neoplasm of early childhood which is classified on its morphologic features into four types (IR, I, II and III) with tumor progression over time within the first 4–5 years of life from the prognostically favorable cystic type I to the unfavorable solid type III. Following the initial report of PPB, its association with other cystic neoplasms was demonstrated in family studies. The detection of the germline mutation in DICER1 provided the opportunity to identify and continue to recognize a number seemingly unrelated extrapulmonary neoplasms: Sertoli-Leydig cell tumor, gynandroblastoma, embryonal rhabdomyosarcomas of the cervix and other sites, multinodular goiter, differentiated and poorly differentiated thyroid carcinoma, cervical-thyroid teratoma, cystic nephroma-anaplastic sarcoma of kidney, nasal chondromesenchymal hamartoma, intestinal juvenile-like hamartomatous polyp, ciliary body medulloepithelioma, pituitary blastoma, pineoblastoma, primary central nervous system sarcoma, embryonal tumor with multilayered rosettes-like cerebellar tumor, PPB-like peritoneal sarcoma, DICER1-associated presacral malignant teratoid neoplasm and other non-neoplastic associations. Each of these neoplasms is characterized by a second somatic mutation in DICER1. In this review, we have summarized the salient clinicopathologic aspects of these tumors whose histopathologic features have several overlapping morphologic attributes particularly the primitive mesenchyme often with rhabdomyoblastic and chondroid differentiation and an uncommitted spindle cell pattern. Several of these tumors have an initial cystic stage from which there is progression to a high grade, complex patterned neoplasm. These pathologic findings in the appropriate clinical setting should serve to alert the pathologist to the possibility of a DICER1-associated neoplasm and initiate appropriate testing on the neoplasm and to alert the clinician about the concern for a DICER1 mutation.

Benign Cutaneous Tumors

Tumors of the cutaneous surface may arise from the epidermis, dermis, or subcutaneous tissue or from any of the specialized cell types in the skin or its appendages. Broad categories include tumors derived from epithelial, melanocytic, or connective tissue structures. Within each location or cell type, lesions are classified as benign, malignant, or, in certain cases, premalignant. Benign epithelial tumors include tumors of the surface epidermis that form keratin, tumors of the epidermal appendages, and cysts of the skin. Melanocytic (pigment-forming) lesions are very common. One of the most frequently encountered forms is the nevus cell nevus. Tumors that are derived from connective tissue include fibromas, histiocytomas, lipomas, leiomyomas, and hemangiomas. This chapter provides an overview of each type of tumor, including sections on epithelial tumors, tumors of the epidermal appendages, familial tumor syndromes, melanocytic tumors, neural tumors, connective tissue tumors, vascular birthmarks, acquired vascular disorders, Kimura disease, lipoma, leiomyoma, and lymphangioma circumscriptum. The sections discuss various forms and their diagnosis, differential diagnosis, and treatment. Figures accompany the descriptions. This chapter contains 83 references, 26 highly rendered figures, and 5 MCQs.

Benign Cutaneous Tumors

Tumors of the cutaneous surface may arise from the epidermis, dermis, or subcutaneous tissue or from any of the specialized cell types in the skin or its appendages. Broad categories include tumors derived from epithelial, melanocytic, or connective tissue structures. Within each location or cell type, lesions are classified as benign, malignant, or, in certain cases, premalignant. Benign epithelial tumors include tumors of the surface epidermis that form keratin, tumors of the epidermal appendages, and cysts of the skin. Melanocytic (pigment-forming) lesions are very common. One of the most frequently encountered forms is the nevus cell nevus. Tumors that are derived from connective tissue include fibromas, histiocytomas, lipomas, leiomyomas, and hemangiomas. This chapter provides an overview of each type of tumor, including sections on epithelial tumors, tumors of the epidermal appendages, familial tumor syndromes, melanocytic tumors, neural tumors, connective tissue tumors, vascular birthmarks, acquired vascular disorders, Kimura disease, lipoma, leiomyoma, and lymphangioma circumscriptum. The sections discuss various forms and their diagnosis, differential diagnosis, and treatment. Figures accompany the descriptions. This chapter contains 83 references, 26 highly rendered figures, and 5 MCQs.