A comparative study of reducing the extracellular potassium concentration in red blood cells by washing and by reduction of additive solution.

BACKGROUND: Extracellular potassium concentration (K(+)) increases in the supernatant of whole and packed red blood cell units (pRBCs) with duration of refrigerated storage in citrate-phosphate-dextrose-adenine (CPDA-1) and additive solution (AS). Studies have shown that to avoid hyperkalemia, washed pRBCs are preferred if relatively fresh pRBCs are not available. To determine whether a simpler procedure, AS reduction, results in lowering of K(+) in pRBCs comparable to that achieved by washing, the K(+) levels by both methods were compared. STUDY DESIGN AND METHODS: Pre- and post-K(+) levels were measured in 6 washed and 11 AS-reduced pRBC units. Each unit was weighed, hematocrit was determined, K(+) was measured, and total K(+) was calculated. Washed units were 3 to 21 and AS-reduced units were 4 to 30 days old. Statistical analysis was performed with a t test. RESULTS: There was no significant difference (p > 0.35) in the initial K(+) between the two groups (mean +/- SD, 36.95 +/- 13.16 mEq/L before washing and 39.78 +/- 19.94 mEq/L before AS reduction). Washing and AS reduction both led to a significant decrease in K(+) levels (2.15 +/- 0.10 mEq/L after washing and 4.41 +/- 3.04 mEq/L after AS reduction, each p < 0.0005). Washing, however, was significantly better than AS reduction in reducing K(+) in stored pRBCs (p < 0.05). CONCLUSIONS: Washing pRBCs results in very low levels of K(+). AS reduction also significantly reduces K(+) levels. Selection of the method of K(+) reduction will depend on the stringency of K(+) reduction needed, the time constraints, and the availability of facilities and staff for washing.

Primary cutaneous mucinous carcinoma: presence of myoepithelial cells as a clue to the cutaneous origin.

BACKGROUND: Primary cutaneous mucinous carcinoma (PCMC) is a rare malignancy with probable apocrine differentiation. It is important to differentiate it from metastatic mucinous carcinoma (MMC), especially from the breast. The histologic and immunohistochemical features overlap between PCMC and breast mucinous carcinomas. In this study, we introduce the presence of myoepithelial component in PCMC as a new morphologic parameter to distinguish it from MMC from either breast or sites elsewhere in the body. MATERIALS AND METHODS: We studied 7 cases of PCMC. The possible in situ component in the tumor was assessed by the presence of a peripheral myoepithelial cell layer. Myoepithelial cell differentiation was confirmed with immunohistochemical stains for p63, CK 5/6, calponin, smooth muscle actin (SMA), HHF-35, and CD10. Estrogen and progesterone receptor (ER/PR), gross cystic disease fluid protein (GCDFP 15), CK7, CK20, and S-100 immunostains were also performed. RESULTS: Histologically, multiple small monomorphic epithelial islands floating in multilocular pools of mucin characterized the tumor. Focally, epithelial islands were bordered by dermal connective tissue at the periphery of mucin pools. Secretory snouts were apparent in all cases providing evidence for apocrine differentiation. In 5 of the 7 cases, an in situ component was identified as epithelial islands being bounded by a myoepithelial layer, which was highlighted by p63, CK 5/6, calponin, SMA, and HHF-35. ER/PR and CK7 were positive in all the cases. GCDFP-15 and CD10 were focally positive in the tumor cells and myoepithelial cells, respectively. All 7 cases were negative for S-100 and CK 20. CONCLUSION: We conclude that an in situ component is frequently present in PCMC (5/7) and may help in distinguishing this entity from MMC, especially of breast origin. Furthermore, it may provide insight into the pathogenetic mechanism of mucinous carcinoma evolving from in situ carcinoma with luminal mucinous distention to cellular tumor with a little surrounding mucin.