These lesions are often limited to the dermis but can extend into the surrounding subcutaneous tissue and/or epidermis. Rarely, the lesions, termed pyrogenic variants, are rich in polymorphonuclear neutrophils. The neoplastic cells strongly express CD30 (100% of cases), CD2 (78%), CD4 (54–90% of cases), cytotoxicity marker proteins, and various other marker proteins that help distinguish it from other ALCL, cutaneous T-cell lymphomas, and cancers. While these cells typically are ALK-negative, they do express ALK-containing fusion proteins in rare cases. The latter cases have a relatively benign course compared to ALK-positive ALCL and are treated as variants of pcALCL rather than ALK-positive ALCL. Gene and molecular abnormalities
Similar to ALK-negative ALCL, pcALCL have chromosomal rearrangements in their DUSP22 (20-30% of cases) and TP63 (5% of cases) genes and a mutation in the MSC (i.e. musculin) gene (6% of cases). Between 1993 and 2019, the Dutch registry had 6 (i.e. 2%) of 319 pcALCL cases that expressed ALK. Three of these cases were due to the NPM1-ALK chimeric gene that predominates in ALK-positive ALCL while the remaining three were due to TRAF1-ALK, ATIC-ALK, or TPM3-ALK chimeric genes. All 6 patients shared exactly the same breakpoint site in the ALK at exon 20 on the ALK gene. Treatment and prognosis
Most pcALCL individuals present with isolated lesions that are effectively managed with radical surgical excision and/or radiation therapies; this approach is regarded as front-line therapy for localized  disease. However, individuals with extensive disease and/or multiple tissue involvement respond poorly to front line treatment.
Nonetheless, the disease has a 10-year overall survival rate of 90%. Typically leg involvement portends a worse prognosis: it has a five-year disease-specific survival rate of 76 percent compared with 96 percent for disease in other locations. Involvement of local nodes alone in patients with skin lesions does not seem to portend an adverse prognosis. Breast implant-associated anaplastic large cell lymphoma
Signs and symptoms
BIA-ALCL is a complication of silicon-filled and saline-filled breast implants which develops 9 years to 10 years (median times) after surgical implantation. First described in 1997, it is estimated that the prevalence of BIA-ACLC in individuals with implants that have a textured surface is 1 in 30,000 while the risk of it is 70-fold lower in individuals who have a smooth surface implant or have no implant at all (i.e. in patients that have another type of ALCL). These relations strongly suggest that BIA-ACLC develops primarily if not exclusively in patients with textured implants. In all cases, however, many researchers suspect that  BIA-ALCL is an under-recognized, misdiagnosed, and under-reported complication of breast implants. Two-thirds of individuals with BIA-ALCL present with swelling, discomfort, and/or (rarely) pain in the affected breast. This is due to the development of a tumor mass and/or swelling caused by an effusion (i.e. fluid) that accumulates between the breast implant surface and the fibrous capsule that has grown around it. The effusion fluid typically contains white blood cells, tumor cells, and high levels of protein.