Margaret Merola

Neural and Neuroendocrine Neoplasms

Clinical: Benign reactive proliferation of nerves and fibroblasts in response to trauma. Often presents as a small, firm painful lesion typically associated with trauma found at any age or body site.

Vascular Neoplasms and Malformations

This chapter will cover vascular anomalies according to the subcategories of vascular neoplasms (benign and malignant), vascular neoplasms of uncertain behavior, vascular malformations and vascular dilatations. Importantly vascular neoplasms are regarded as lesions, which undergo cellular proliferations, while vascular malformations are the result of aberrations in morphogenesis.

Vasculitic and Vasculopathic Disorders

This chapter is organized according to large, medium and small vessel vasculitis as proposed by the Chapel Hill Consensus Conference on the nomenclature of systemic vasculitis. The subset of small vessel vasculitic lesions will be addressed according to the predominant inflammatory cell infiltrate or feature (neutrophilic, urticarial, fibrosing, lymphocytic and granulomatous). The final section will address neutrophilic dermatoses and vasculopathies.

Drug Reaction Patterns

Reactions to drugs can vary quite a bit clinically as well as histopathologically. The different types of drug reactions will be grouped below according to their clinical name or histological pattern. Although they will be listed by histological reactions pattern(s), an attempt has been made to list them in decreasing order of incidence. The four most common drug reactions in the skin are morbilliform (exanthematous), urticarial, fixed drug, and the erythema multiforme/Stevens-Johnson syndrome/toxic epidermal necrolysis spectrum.

Cutaneous Lymphomas and Hematopathology

Lymphomas and non-neoplastic infiltrates of the skin are not uncommon lesions to encounter in routine dermatopathology specimens. When confronted with these entities in routine hematopathology practice (bone marrow biopsies and lymph nodes), diagnosis of hematopoietic neoplasms depends first on recognizing the overall architectural pattern. Analogous to their lymph node and bone marrow counterparts, diagnosis of cutaneous lymphomas and other malignant hematopoietic proliferations depends in part on the pattern of infiltration. Certain lymphomas have the propensity to form nodular aggregates while others invade in diffuse sheets of malignant cells. There are lymphomas that preferentially involve the epidermis and superficial dermis and those that arise primarily in the subcutaneous tissue. Given that skin contains numerous blood vessels and adnexal structures, infiltrates can either primarily or secondarily involve these compartments in varying degrees. After pattern determination, the diagnostician must also decide the size of the malignant cells since some tumors are comprised of small cells, others large cells, and still others mixed cell populations. The background milieu is also important: Are there lymphocytes, plasma cells, eosinophils, neutrophils, or perhaps histiocytes? All of these elements should be taken into consideration before the application of immunohistochemical stains, cytochemical stains, flow cytometry, or gene rearrangements.

Granulomatous (Non-infectious) Diseases

Clinical: Sarcoidosis is a common systemic disease which can affect nearly any organ system. Lungs, lymph nodes, and skin are the most frequently involved organs. Although typically indolent, spread into the central nervous system or heart can have high morbidity and mortality rates. It has a predilection for African-American and Hispanic patients. Asians are rarely affected. Sarcoidosis can present at any age, but adults are most often affected, particularly if there is skin involvement.

Epidermal Maturation Disorders

Clinical: Most common ichthyosis due to autosomal dominant profilaggrin mutation that presents in childhood with fine, white dry scaling skin resembling “fish scales” on pretibial and other extensor surfaces with sparing of antecubital and popliteal flexural areas. May be seen in conjunction with atopic dermatitis (also associated with profilaggrin mutations). Acquired ichthyosis presents in adults, most typically in the lower extremities, otherwise, clinically and histologically similar to icthyosis vulgaris.

Parasitic Infections and Bite Reactions

Clinical: Insect bites clinically appear as excoriated, pruritic papules, nodules, erosions, bullae, vesicles, erosions or ulcers.

Metabolic and Depositional Disorders

Clinical: Comprised of a group of disorders with abnormal deposition of calcium salts in the skin presenting as white papules or nodules. Classically subdivided according to etiology: dystrophic (due to abnormal connective tissue), metastatic (due to elevated serum calcium and/or phosphate), and idiopathic, although some overlap occurs.

Interface (Lichenoid) Dermatoses

Clinical: Commonly remembered as the “five P’s” – purple, polygonal, planar, and pruritic papules (and/or plaques) with a fine overlying scale (known as Wickham’s striae). LP commonly manifests as grouped papules on the distal extremities and/or trunk, also with frequent involvement of oral mucosa.