The syndrome is defined by the presence of; both of two major criteria, peripheral neuropathy and a clonal plasma cell dyscrasia (increased bone marrow plasma cells in ~67% of cases; ≥1 plasmacytoma in ~33% of cases); at least one other major criteria (Castlemans disease, sclerotic bone lesions, elevated serum levels of the cytokine VEGF); and at least one minor criterion (organomegaly, extravascular volume overload [e.g. ascites, edema, pleural effusion, and/or pericardial effusion], endocrinopathy [i.e. hypogonadism, defects in the hypothalamic–pituitary–adrenal axis], skin changes, papilledema, and/or hematological manifestations [i.e. thrombocytosis or polycythemia]). The monoclonal protein in POEMS patients is typically identified as IgA or IgG which in >95% of cases contains a λ chain that is restricted to either of two members of the V lambda 1 subfamily viz., IGLV1-40*01 and IGLV1-44*01 (there are 29 other members in the V lambda family). That is, the myeloma protein in POEMS is almost invariably a clonal λ light chain variant. Deletion of chromosome 13 and chromosomal translocations but not increases in chromosome number have also been reported to occur in POEMS patients.Patients with 1 or 2 isolated plasmacytomas have been successfully treated with targeted radiotherapy to obtain relief of symptoms and sometimes complete remission of disease. (Isolated plasmacytomas may regress spontaneously.) Patients with >2 plasmacytomas or symptomatic disseminated disease have been treated with chemotherapy often followed by autologous stem-cell transplantation; these treatments have been found to reduce symptoms of the disease and lead to long-term partial remissions of disease.
Hidradenoma refers to a benign adnexal tumor of the apical sweat gland. These are 1–3 cm translucent blue cystic nodules. It usually presents as a single, small skin-colored lesion, and may be considered closely related to or a variant of poromas. Hidradenomas are often sub-classified based on subtle histologic differences, for example:
Eccrine acrospiroma
Clear-cell hidradenoma or acrospiroma
Nodular hidradenoma or acrospiroma
Solid-cystic hidradenomaDiscussion of sweat gland tumors can be difficult and confusing due to the complex classification and redundant terminology used to describe the same tumors. For example, acrospiroma and hidradenoma are synonymous, and sometimes the term acrospiroma is used to generally describe benign sweat gland tumors. In addition, a single lesion may contain a mixture of cell-types. There has also been a change in understanding about how tumors that were previously believed to strictly derive from specific sweat gland types may, in fact, derive from both eccrine or apocrine glands.Hidradenomas are by definition benign, with malignant transformation very rare. When tumors show malignant characteristics, they are known as hidradenocarcinoma. Surgical excision is usually curative and local recurrences are rare, although malignant tumors may metastasize. See also
Spiroma
List of cutaneous conditions
List of cutaneous neoplasms associated with systemic syndromes

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