Anaplastic large cell lymphoma (ALCL) refers to a group of non-Hodgkin lymphomas in which aberrant T cells proliferate uncontrollably. Considered as a single entity, ALCL is the most common type of peripheral lymphoma and represents ~10% of all peripheral lymphomas in children. The incidence of ALCL is estimated to be 0.25 cases per 100,000 people in the United States of America. There are four distinct types of anaplastic large cell lymphomas that on microscopic examination share certain key histopathological features and tumor marker proteins. However, the four types have very different clinical presentations, gene abnormalities, prognoses, and/or treatments.ALCL is defined based on microscopic histopathological examination of involved tissues which shows the presence of at least some ALCL-defining pleomorphic cells. These "hallmark" cells have abnormal kidney-shaped or horseshoe-shaped nuclei, prominent Golgi, and express the CD30 tumor marker protein on their surface membranes. In 2016, the World Health Organization (WHO) separated ALCL into four types: ALK-positive ALCL (also termed ALK+ ALCL), ALK-negative ALCL (ALK− ALCL), primary cutaneous ALCL (pcALCL), and breast implant-associated ALCL (BIA-ALCL). WHO defined BIA-ALCL as an ALCL type provisionally, i.e. subject to redefinition if future studies should support such a change.ALK-positive and ALK-negative ALCL are aggressive systemic lymphomas. They are differentiated based on their expression of an abnormal ALK protein made by a somatic recombination in the ALK gene. ALK, i.e. anaplastic lymphoma kinase, is a protein product of the ALK gene located on chromosome 2.
Midline cervical clefts are a rare congenital anomaly resulting from incomplete fusion during embryogenesis of the first and second branchial arches in the ventral midline of the neck. The condition presents as a midline cutaneous defect of the anterior neck with a skin projection or sinus, or as a subcutaneous erythematous fibrous cord. Surgical excision is the preferred treatment. See also
Accessory tragus
List of cutaneous conditions


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