ABSTRACT Undifferentiated carcinoma of the pancreas with osteoclast-like giant cells (UCOGCs) is an extremely rare morphologically and clinically distinct variant of pancreatic ductal adenocarcinoma (PDAC), exhibiting a characteristic component of reactive osteoclast-like giant cells admixed with neoplastic mononuclear cells. Sommers and Meissner first described it in 1954 as an “unusual carcinoma of the pancreas”. Later it acquired many different names. In 2010, the WHO classified these tumors as a variant of PDAC under the heading of “undifferentiated carcinoma with osteoclast-like giant cells”. Here we describe the first case of pancreatic mixed neuroendocrine-non-neuroendocrine neoplasms (MiNEN) composed of UCOGC and pancreatic neuroendocrine tumor (NET), which occurred in a 78-year-old man with biliary colic and pancreatitis. The mass did not respond to the chemotherapy, and he soon developed liver metastasis from the NET component, and unfortunately, the patient passed away 10 months later. Since UCOGC is extremely rare, and its association with NET has not been reported yet, our case expands the knowledge regarding its unusual presentation and poor prognosis.

ABSTRACT Arteriovenous malformation (AVM) is a rare lesion in the uterus, which can lead to abnormal uterine bleeding. While AVM has been described in other organs in the literature, there is a paucity of pathology reports of the AVM in uterus. On gross examination, the uterus was markedly enlarged and partly distorted with a pedunculated solid mass, which on the cut surface showed multiple well-circumscribed hemorrhagic cysts ranging from 0.1 to 4.0 cm in size. Microscopically, they were malformed dilated vascular structures containing organized thrombi. We present this case of uterine AVM with gross and microscopic findings, which can serve as a crucial reminder for pathologists to keep in the differential diagnoses as a potential cause of abnormal uterine bleeding.

ABSTRACT Ochronosis is a cutaneous disorder caused by the accumulation of phenols, either endogenously as homogentisic acid in patients with alkaptonuria (autosomal recessive disorder with deficiency of the enzyme homogentisic acid oxidase), or exogenously in patients using phenol products such as topical creams containing hydroquinone or the intramuscular application of antimalarial drugs. Exogenous ochronosis (EO) typically affects the face and was reported in patients with dark skin such as Black South Africans or Hispanics who use skin-lightening products containing hydroquinone for extended periods. Recently more cases have been reported worldwide even in patients with lighter skin tones, to include Eastern Indians, Asians, and Europeans. However, just 39 cases of EO have been reported in the US literature from 1983 to 2020. Here we present two cases; a 69 and a 45-year-old female who were seen for melasma, given hydroquinone 4% cream daily and tretinoin 0.05%. Both patients noticed brown spots on their cheeks, which progressively enlarged and darkened in color. The diagnosis of ochronosis was confirmed by characteristic histopathological features on the punch biopsy. Unfortunately, neither patient responded to multiple treatments (to include, tazarotene 0.1% gel and pimecrolimus ointment, topical corticosteroids, and avoidance of hydroquinone containing products). We also present a case of classic (endogenous) ochronosis in a patient with alkaptonuria to picture the histological similarities of these two entities. EO is an important clinical consideration because early diagnosis and treatment may offer the best outcome for this notoriously refractory clinical diagnosis.

ABSTRACT In adults, B-lymphocytes comprise approximately 10% of circulating lymphocytes. The majority of peripheral B cells are B2 cells (“Mature” B-cells), which function as part of the humoral adaptive immune system. B1 cells (“Innate-like” B cells) are another sub-class of B lymphocytes, considered as innate immune cells with a characteristic phenotype (CD20+, CD27+, CD43+, CD70-, CD11b+, sIgM++, sIgD+) which can be divided into two subtypes; B1a (CD5+): spontaneously produce broadly reactive natural IgM, and B1b (CD5-): can generate T-cell independent, long-lasting IgM. There is very limited data available, indicating a correlation between allogeneic bone marrow transplantation and an increase in B1a cells. Here we present a case of a 17-year-old female with homozygous sickle cell disease (HbSS disease) who underwent hematopoietic stem cell transplant (HSCT). Approximately seven months post-transplant, she was found to have 16% immature mononuclear cells on complete blood count (CBC)-differential report. A follow-up peripheral blood flow cytometry showed that these cells were polyclonal CD5+/CD20+ B-cells, and comprised 66% of lymphocytes. Further workup and follow up failed to reveal any lymphoproliferative disorders. It is important not to misdiagnose these cells as an atypical CD5+ lymphoproliferative disorder. The presence of B1a cells has not been widely reported in non-neoplastic post-stem cell transplanted patients. This case also adds to and expands our knowledge regarding the presence of increased circulating B1a cells after stem cell transplant in a patient with no history of hematological malignancy.